The projects encompassed by this application involve the characterization of the immune responsiveness to human colon cancer cells. The system will utilize 3M KCl solubilized antigens from a cultured colon adenocarcinoma cell, established and characterized by the applicant, encapsulated in neutral or charged liposome carriers. Normal peripheral blood mononuclear cells will be co-incubated with soluble antigens, liposome-encapsulated antigens, or antigen-fed macrophage preparations, and subsequently tested for specific antigen-induced blastogenesis or cytotoxicity on target colon tumor cells. The lymphoid cells acting in this in vitro system will be characterized for sheep cell rosettes (active and total T cells) and antibody-mediated killing (K cells). Isoelectric focused soluble tumor antigens will be tested in this system to discern inhibitory and/or stimulatory factors which could modulate the in vitro immunity. The isoelectric fractions which contain tumor-associated antigens, CEA, HLA, and fetal bovine sera and normal bowel antigens have already been identified with heteroantisera. A solid-state radioimmunoassay developed by the applicant will be utilized to characterize isolated histiotypic or individualistic tumor antigens. This approach to study of human tumor resistance, using a novel carrier, the liposome, may provide not only insight into the nature of immune induction by tumor antigens, but also clues to the biochemical and molecular identities of factors modulating immunity to surface antigens. An in vitro system for colon cancer may afford means to monitor tumor-associated antigens or their corresponding antibodies in afflicted patients, act as a screening procedure for purification of tumor-specific antigens, and provide reagents to monitor therapy protocols.